This invention relates to a silicon-aluminum mixed oxide, a process for the production thereof as well as the use as a polishing agent in dispersions which are used, for example, for polishing electronic components, in particular for CMP applications.
The patent specification EP-0 585 544 discloses pulverulent silicon-aluminum mixed oxides produced by flame hydrolysis which are of amorphous structure and have a composition of from 65 to 72.1 wt. % Al2O3 and from 27.9 to 35 wt. % SiO2 and a BET surface area of between 20 and 200 m2/g
The invention provides a silicon-aluminum mixed oxide powder produced by flame hydrolysis and having a composition of from 1 to 99.999 wt. % Al2O3, preferably 40 to 80 wt. % Al2O3, the remainder being SiO2, wherein the powder exhibits an amorphous structure in the X-ray diffraction pattern and consists of intergrown primary particles, and in these primary particles crystallites are present, and these crystallites have sizes of one to 200 namometers and the specific surface area of the powder is 5 to 300 m2/g, preferably 50 to 150 m2/g.
The invention also provides a process for the production of the silicon-aluminum oxide powder produced by flame hydrolysis according to the invention, wherein silicon halide and aluminum halide are vaporized in a particular ratio to one another and are homogeneously mixed with air, oxygen and hydrogen in a mixing unit by means of a carrier gas. This mixture then undergoes combustion in a burner of known construction. After the separation of the solids from the vapour phase, any traces of halide possibly adhering to the product are separated off in a further processing step by means of moist air at elevated temperature.
It has now been found that silicon-aluminum mixed oxides according to the invention which are made into a dispersion exhibit outstanding properties as polishing agents.
These dispersions can be used in particular for polishing in the electronics industry (CMP).